The polarized characteristic of multiphoton process can be used to assign the symmetries of electronic states and vibrational structures. In this paper the polarizing ratios of some kinds of degenerate three-photon transitional tensors are calculated. Besides, the three-photon resonant polarizing ioniza-tion spectra of ethylbenzene are measured. The highly excited electronic state which is responsible for the transition is referred as A" and the vibrational structures of this electronic state are also obtained.